On 08/30/2018 04:15 PM, Jeff Law wrote:
On 08/13/2018 09:21 PM, Martin Sebor wrote:
[PATCH 2/6] detect unterminated const arrays in strlen calls (PR 86552)
The attached changes implement the detection of past-the-end reads
by strlen due to unterminated arguments.
gcc-86552-2.diff
PR tree-optimization/86552 - missing warning for reading past the end
gcc/ChangeLog:
* builtins.c (warn_string_no_nul): New function.
(expand_builtin_strlen): Warn for unterminated arrays.
(fold_builtin_strlen): Add argument. Warn for unterminated arrays.
(fold_builtin_1): Adjust call to fold_builtin_strlen.
* builtins.h (warn_string_no_nul): New function.
gcc/testsuite/ChangeLog:
* gcc.dg/warn-strlen-no-nul.c: New test.
So this has a dependency on parts of the 1/6 patch that haven't been
committed yet.
Ignoring that for the moment (since I have those parts in my tree :-)...
There are minor API changes to functions we need to use. Those are
trivially fixed up.
With that taken care of I get one XPASS from the new test:
+T (v0 ? &b[3][v0] : &b[3][v1]); /* { dg-warning "nul" "bug" { xfail *-*-* }
} */
I haven't dug into why this now passes. It could well be the various
refinements we've made over the last couple weeks.
I'm not sure what's letting it succeed. get_range_strlen() can
tell the array isn't nul-terminated but it's only called from
gimple_fold_builtin_strlen() which doesn't warn. The next
chance to warn is handle_builtin_strlen() but it doesn't call
get_range_strlen(). The next opportunity to warn after that
is expand_builtin_strlen() and it doesn't call get_range_strlen()
either. There definitely are more opportunities to warn as
the many xfails in the warn-strlen-no-nul.c test indicate.
I didn't want to make the initial patch too bin and intrusive
by handling all those cases but it's something I'd like to do
in a followup.
Given that I've got the patch in my tree I'll take care of posting the
final version of the patch and committing it once I've committed the
prereqs.
Sounds good. Thanks for handling that!
Martin
